The aim of this research is to determine how premotor circuitry generates vocal patterns, and to compare differences in females and males that lead to sexually distinct vocalizations. Information relating neuronal function with vocalization is essential to understanding phonation and disorders such as dysarthrias. While forebrain pattern generators have been well characterized in other systems, medullary circuits producing vocalizations remain poorly understood. Because Xenopus vocalization is emancipated from respiration, vocalization is simplified relative to other vertebrates: this feature provides an experimentally tractable vertebrate system in which to study premotor circuitry in the medulla. A parabrachial nucleus homologue, DTAM, projects to laryngeal motor nucleus motoneurons and interneurons. Nerve activity during DTAM stimulation will be analyzed to assess how premotor patterns are shaped into motor output. Intracellular recordings of motoneurons and interneurons will be also be made during DTAM stimulation. Results will determine of what types of input each neuron receives, and whether motoneurons and interneurons respond differentially to DTAM signals. It will also be possible to assess whether DTAM inputs to the motor nucleus are sexually distinct. Finally, chronic single-unit recordings of DTAM neurons in singing frogs will be used to determine activity patterns during each call. These studies should provide insight into how vocalizations are produced and what properties of the neural circuitry underly sex-specific behaviors.